Abstract

Background

Lung cancer is one of the most malignant tumors, representing a significant threat
to human health. Lung cancer patients often exhibit tumor cell invasion and metastasis
before diagnosis which often render current treatments ineffective. Here, we investigated
the effect of staurosporine, a potent protein kinase C (PKC) inhibitor on the mobility
and invasiveness of human lung adenocarcinoma A549 cells.

Methods

All experiments were conducted using human lung adenocarcinoma A549 cells that were
either untreated or treated with 1 nmol/L, 10 nmol/L, or 100 nmol/L staurosporine.
Electron microscopy analyses were performed to study ultrastructural differences between
untreated A549 cells and A549 cells treated with staurosporine. The effect of staurosporine
on the mobility and invasiveness of A549 was tested using Transwell chambers. Western
blot analyses were performed to study the effect of staurosporine on the levels of
PKC-α, integrin β1, E-cadherin, and LnR. Changes in MMP-9 and uPA levels were identified
by fluorescence microscopy.

Results

We demonstrated that treatment of A549 cells with staurosporine caused alterations
in the cell shape and morphology. Untreated cells were primarily short spindle- and
triangle-shaped in contrast to staurosporine treated cells which were retracted and
round-shaped. The latter showed signs of apoptosis, including vacuole fragmentation,
chromatin degeneration, and a decrease in the number of microvilli at the surface
of the cells. The A549 cell adhesion, mobility, and invasiveness significantly decreased
with higher staurosporine concentrations. E-cadherin, integrin β1, and LnR levels
changed by a factor of 1.5, 0.74, and 0.73, respectively compared to untreated cells.
In addition, the levels of MMP-9 and uPA decreased in cells treated with staurosporine.

Conclusion

In summary, this study demonstrates that staurosporine inhibits cell adhesion, mobility,
and invasion of A549 cells. The staurosporine-mediated inhibition of PKC-α, induction
of E-Cad expression, and decreased integrin β1, LnR, MMP-9, and uPA levels could all
possibly contribute to this biological process. These results represent a significant
step forward in the ongoing effort to understand the development of lung carcinoma
and to design novel strategies to inhibit metastasis of the tumor by targeting the
cell-adhesion, mobility and invasion of tumor cells.